Add a test for default toString behavior.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1091075 13f79535-47bb-0310-9956-ffa450edef68

src/test/java/org/apache/commons/lang3/PairTest.java

@@ -57,4 +57,10 @@ public class PairTest {
         assertFalse(pair.equals(pair2));
         assertFalse(pair.hashCode() == pair2.hashCode());
     }
+
+    @Test
+    public void testToString() throws Exception {
+        Pair<String, String> pair = Pair.of("Key", "Value");
+        assertEquals("ImmutablePair(Key,Value)", pair.toString());
+    }
 }